1. Field of the Invention
The invention relates in general to a touch control system, and more particularly, to a touch control system having multiple sensing regions.
2. Description of the Related Art
Operating interfaces of recent electronic products have become increasingly user-friendly and intuitive with the progressing technology. For example, through a touch screen, a user can directly interact with applications as well as input messages/texts/patterns with fingers or a stylus, thus eliminating complexities associated with other input devices such as a keyboard or buttons. In practice, a touch screen usually comprises a touch panel and a display provided at the back of the touch panel. According to a touch position on the touch panel and a currently displayed image on the display, an electronic device determines an intention of the touch to execute corresponding operations.
Existing capacitive touch sensing techniques can be roughly categorized into self capacitive and mutual capacitive types. Compared to mutual-capacitive touch panels, self capacitive touch panels can be implemented through a single-layer electrode with a simpler manufacturing process and lower costs, and thus prevail in many entry-level electronic products.
FIG. 1 shows a common self capacitive touch panel. In a sensing region 100 represented by a dotted frame, a plurality of electrodes (e.g., electrodes 11, 12, 13 and 14) having equal widths and similar to right triangles are disposed. In this example, each of the electrode is connected to a sensor (to keep the diagram clear, only a first sensor 15 connected to the electrode 11 and a first sensor 16 connected to the electrode 13 are depicted as a representative). The sensors detect capacitance changes of the electrodes, and provide detection results to a controller (not shown), which then accordingly determines a position of a user touch. The controller may calculate coordinates (x, y) of the position of the user touch according to the equations below:
      x    =                            ∑                      i            =            1                    N                ⁢                                  ⁢                  (                                    C              i                        *                          X              i                                )                                      ∑                      i            =            1                    N                ⁢                                  ⁢                  C          i                      ,
In the above equations, N represents a total number of the sensors, i is an integral index between 1 and N, Ci represents a capacitance change detected by an ith sensor, Xi represents an X-coordinate of a centroid of the electrode connected the ith sensor, and Yi represents a Y-coordinate of a centroid of the electrode connected the ith sensor.
To expand a touch control area, an electrode arrangement forming multiple sensing regions shown in FIG. 2 is developed. As shown in FIG. 2, the electrodes are divided into upper and lower groups in the Y-direction to form two different sensing regions 210 and 220. In the prior art, a controller regards the sensing regions 210 and 220 as two independent regions, and considers capacitance changes in the two sensing regions individually. A setback of such approach is that, when a position of a user touch simultaneously covers both of the sensing region 210 and the sensing region 220, a misjudged result is likely incurred. For example, when the user touch falls at a position represented by a dotted circle in FIG. 3(A), the controller may interpret the touch point as two smaller touch points 30A and 30B depicted in FIG. 3(B). The above detection error at border regions of a sensing region may lead the controller to misjudge an intention of the user touch and thus trigger an erroneous operation result.